So I like some mildly sick shit. Not the worst (no actual shit, thankyouverymuch), but I get hit, cut, demeaned, restrained, and "forced" into sex acts, and I really really get off on it.
Why? Various theories. Fundamental neurological miswiring, weird childhood experiences, normalizing/encouragement from kinky friends, low self-esteem, reading too many vampire romance novels, escaping real-life responsibilities, bowing to the will of the Patriarchy. (That last one doesn't explain why I think about bondage when I masturbate--now that's internalizing!)
I do think about it but honesty I don't understand why. It feels so physically good to me that it's hard for me to accept a purely psychological explanation. When I'm getting beat up by a boy, my thoughts aren't at all complex or half-bad--all I'm really thinking is "gosh this is so exciting and fun." And my pussy is getting wet. I know psychology can do weird things to a person but the way I respond to pain makes me really think that I was just born this way. I don't remember making a conscious choice to be a masochist--but I do remember being about ten years old and thinking about torture when I masturbated.
At the same time, I grew up in a culture, I had friends and partners, I watched porn; I can't claim to have invented my entire sexuality myself. "Hurty is sexy" might be inborn but I don't think that leather or rope or buttplugged blowjobs were my ideas. So I have been influenced, but it's not at all clear to me how much--did the culture merely give me a script in which I could fulfill my desires, or did it actually change my desires? I don't know.
However, while not dismissing the value of introspection, I don't think there's any reason to stop having pervsex just because I don't know why I do it. What I do know is that I honestly, thoroughly enjoy it for its own sake. And I've never felt any ill effects or seen any in my partners--not only do I feel good during a scene, but I feel good afterwards. Then two days later when I'm all cooled off and I think about what I did, I still feel good.
Or maybe the whole idea that it even needs such thorough understanding is bunk. I haven't performed a full soul-search into why I like photography or country music or desert landscapes. I just... found out I liked them, figured they weren't hurting anybody, and had fun. It's a joy to find something that really makes you take pleasure in life, no matter what it is.